1. Technical Field
The present invention relates to a method of operating an inkjet head.
2. Description of the Related Art
In an inkjet head, printing is performed by operating a membrane, which forms a part of a pressure and holds the ink in the pressure chamber, such that it compresses the pressure chamber, whereby ink droplets are ejected through nozzles connected to the pressure chamber.
The operation of the membrane is achieved by adjusting the voltage delivered to actuators joined to the membrane, where the series of operating signals, i.e. the form of operating waveform, transmitted to the actuators has a great impact on the size, the ejection speed, and stability of the ink droplets ejected. These ejection properties of the ink droplets may show different trends, even when actuators are operated by delivering the same operating waveforms, according to the internal structure of the inkjet head, shape of the actuators, size of the nozzles, and properties of the ink. Therefore, a method of maximizing the performance of an inkjet head would be to identify the properties of the inkjet head and then deliver an optimized waveform to the actuators.
FIGS. 1 to 3 are graphs illustrating operating waveforms for inkjet heads according to prior art. By delivering a pulse waveform once more at the final portion of the waveform, as shown in FIG. 1, to provide a smooth motion of the actuators, it is possible to efficiently suppress the vibration of the menisci and provide a stable ejection of ink droplets through a required diameter. However, this method is limited in that it considers only the relationship between the operating waveform and the resonance of the actuators.
In the approach shown in FIG. 2, the operating waveform is formed to correspond with the resonance period (Ta) of the actuators or the resonance period (Tc) of the pressure chamber, whereby the vibration of the menisci may be suppressed and the ejection of the ink droplets may be stabilized.
FIG. 3 shows an operating waveform with which both small and large droplets can be made in nozzles having a large diameter, to compensate for the fact that a small diameter of the nozzles, for improving disintegrating ability to provide minute ink droplets, slows down the speed, whereas a large diameter of the nozzles, for increasing speed, degrades the disintegrating ability.
However, the operating waveforms for inkjet heads described above do not provide a series of waveforms spanning the entire resonance period of the inkjet head that considers the respective resonance frequencies of the actuators, pressure chamber, and menisci, for ejecting ink droplets of a desired size at high speeds.